A skeleton found walled-up in a basement full of junk has been identified as a first-grade teacher reported missing by her husband more than 27 years ago.

JoAnn Nichols disappeared in December 1985.

Her husband James Nichols died of natural causes last December, aged 82.

Authorities say a contractor cleaning hoarded items and debris out of the Nichols' home in upstate New York found the bones in a sealed container behind a false basement wall.

The Dutchess County medical examiner's office identified the remains as those of JoAnn Nichols, based on dental records.

Dr Kari Reiber said the 55-year-old woman died from a blow to the head.

Poughkeepsie Police say the cold case has now been reopened and new evidence is being examined in the lab.

According to archives of the Poughkeepsie Journal newspaper, JoAnn Nichols taught her last day of school on December 20, 1985.

She did not show up for a hair appointment the next day, and that afternoon, a minister called police on James Nichols' behalf to report her missing.

James Nichols told detectives he last saw his wife when he left for work at IBM that morning, and that he found a typed note when he got home.

There was speculation that JoAnn Nichols was despondent over their only child's drowning death three years earlier, when he was 25.

A detective told the Journal a few months later that the note indicated a "degree of depression, but it's not what I'd consider a suicide letter".

Police searched nearby rivers but found no trace of the missing woman.

Nichols told police he found his wife's locked car on December 22 at a nearby shopping centre.

Then-Detective Lt Charles Mittelstaedt told the Journal there was no evidence of foul play. He said four detectives were working the case full time.

Nichols later told a reporter that his wife called him early on Christmas Eve morning to say she was OK and that he should say hello to their two golden retrievers for her. He said he asked where she was, and she hung up.

"There's no reason to assume she's dead or alive, joined a group or run off with some other man. There are a thousand possibilities. The pain is not knowing," the Journal quoted Nichols as saying in an interview.

Jeannie Foster, 71, a longtime friend of the couple, told the Journal she never suspected James Nichols in his wife's disappearance.

She described JoAnne as down-to-earth and a delight to be with.

But she said James was odd and once showed guests the frozen carcass of a pet cat he kept in a basement freezer.